Fresh on the heels of the announcement last week that China was threatening to cancel orders for 9 billion euros worth of orders for Airbus jetliners, seven of Europe’s leading aviation companies have joined forces this week to formally oppose the European Union’s tax on airline emissions designed to combat global warming.

This joint action raises the stakes in what has become a major battle over Brussels’ drive to curb carbon pollution by taxing airlines operating over European territory, regardless of the flight’s point of origin. See “European Affairs” article for detailed background on the airline emissions debate. The appeal by Airbus and six other airlines came in letters to European political leaders including Britain’s David Cameron, Germany’s Angela Merkel and France’s Francois Fillon asking them to urge the EU to put the measure “on hold.” The initiative is also backed by top executives of British Airways, Virgin Atlantic, Lufthansa, Air France, Air Berlin and Iberia. The heads of two makers of aerospace engines, Safran of France and MTU of Germany, also signed the letters.

The US and Russia are also on record as opposing the emissions tax. Last year the US lost a legal challenge at the European Court of Justice, which ruled that the tax was legal under EU and international law. The US House of Representative in the meantime has passed a bill with bi-partisan support that would make it illegal for US carriers to participate, or pay, in the emission tax scheme. The matter is pending in the US Senate. House Subcommittee Chair John L. Mica (R-FL) called the EU measure “a violation of US sovereignty.”

The EU has resolutely defended the measure. After winning the court case in December an EU spokesperson said: “We will neither abandon nor delay it.”